Extreme Wind Events Influence Seed Rain and Seedling Dynamics of Guam’s Serianthes nelsonii Merr

The seasonal aspects of Guam’s Serianthes nelsonii seed rain quantity, new seedling emergence, and lifespan of newly emerged seedlings were determined by direct observations. Two high wind events in January and September 2013 generated 63% of the annual number of new seeds collected in litterfall. A defoliating tropical cyclone in May 2015 generated an abrupt increase in seedling emergence with 17% of the annual new seedling count emerging during the 4-week period after the tropical cyclone. Of the annual count of seedlings that lived longer than 2 weeks, 8% of them emerged during the 7 months prior to the tropical cyclone in May 2015. In contrast, 92% of these long-lived seedlings emerged during the 5 months immediately after the tropical cyclone. Mitigating the limitations to regeneration and recruitment of Serianthes nelsonii will likely require a change in approach for species recovery such that holistic habitat restoration becomes the goal rather than species recovery per se.

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The Extreme Wind Events in the Ross Island Region of Antarctica

Weather and Forecasting ◽

10.1175/waf-d-15-0125.1 ◽

2016 ◽

Vol 31 (3) ◽

pp. 985-1000 ◽

Cited By ~ 1

Author(s):

Nicholas J. Weber ◽

Matthew A. Lazzara ◽

Linda M. Keller ◽

John J. Cassano

Keyword(s):

Structural Damage ◽

Ross Sea ◽

Enso Event ◽

Central Pacific ◽

Island Region ◽

Back Trajectories ◽

Extreme Wind ◽

Mcmurdo Station ◽

Wind Events ◽

Upper Level

Abstract Numerous incidents of structural damage at the U.S. Antarctic Program’s (USAP) McMurdo Station due to extreme wind events (EWEs) have been reported over the past decade. Utilizing nearly 20 yr (~1992–2013) of University of Wisconsin automatic weather station (AWS) data from three different stations in the Ross Island region (Pegasus North, Pegasus South, and Willie Field), statistical analysis shows no significant trends in EWE frequency, intensity, or duration. EWEs more frequently occur during the transition seasons. To assess the dynamical environment of these EWEs, Antarctic Mesoscale Prediction System (AMPS) forecast back trajectories are computed and analyzed in conjunction with several other AMPS fields for the strongest events at McMurdo Station. The synoptic analysis reveals that McMurdo Station EWEs are nearly always associated with strong southerly flow due to an approaching Ross Sea cyclone and an upper-level trough around Cape Adare. A Ross Ice Shelf air stream (RAS) environment is created with enhanced barrier winds along the Transantarctic Mountains, downslope winds in the lee of the glaciers and local topography, and a tip jet effect around Ross Island. The position and intensity of these Ross Sea cyclones are most influenced by the occurrence of a central Pacific ENSO event, which causes the upper-level trough to move westward. An approaching surface cyclone would then be in position to trigger an event, depending on how the wind direction and speed impinges on the complex topography around McMurdo Station.

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Extreme winds in a WRF downscaling for the SAM-22 CORDEX domain for the 1979-2018 Historical Period

10.5194/egusphere-egu21-10363 ◽

2021 ◽

Author(s):

Natalia Pillar da Silva ◽

Rosmeri Porfírio da Rocha ◽

Natália Machado Crespo ◽

Ricardo de Camargo ◽

Jose Antonio Moreira Lima ◽

...

Keyword(s):

Wind Speed ◽

Oil And Gas ◽

Offshore Structures ◽

Horizontal Resolution ◽

Historical Period ◽

Climate Projections ◽

Wind Speeds ◽

Extreme Wind ◽

Wind Events ◽

Extreme Winds

<p>This study aims to evaluate how extreme winds (above the 95th percentile) are represented in a downscaling using the regional model WRF over the CORDEX South American domain in an approximate 25 km (0.22 degrees) horizontal resolution, along with CFSR as input. The main focus of the analysis resides over the coastal Brazilian region, given a large number of offshore structures from oil and gas industries subject to impact by severe events. Model results are compared with a reanalysis product (ERA5), &#160;estimates from satellites product (Cross-Calibrated Multi-Platform Wind Speed), and available buoy data (Brazilian National Buoy Project). Downscaling results from WRF show an underestimation of maximum and extreme wind speeds over the region when compared to all references, along with overestimation in the continental areas. This directly impacts results for extreme value estimation for a larger return period and severity evaluation of extreme wind events in future climate projections. To address this, a correction procedure based on the linear relationship between severe wind from satellite and model results is applied. After linearly corrected, the extreme and maximum wind speed values increase and errors in the representation of severe events are reduced in the downscaling results.</p>

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Seed production and seedbank dynamics in subthreshold velvetleaf (Abutilon theophrasti) populations

Weed Science ◽

10.1017/s0043174500092511 ◽

1997 ◽

Vol 45 (1) ◽

pp. 85-90 ◽

Cited By ~ 26

Author(s):

John Cardina ◽

Heather M. Norquay

Keyword(s):

Pest Management ◽

Seed Production ◽

Weed Management ◽

Seedling Emergence ◽

Seed Rain ◽

Abutilon Theophrasti ◽

No Tillage ◽

Single Seed ◽

No Till ◽

The Impact

The impact of seed production by subthreshold weed populations on future weed problems has impeded the adoption of integrated pest-management principles for weed management. Studies were conducted in fields with no velvetleaf history to determine how seedbanks and seedling populations change following seed production 1 yr or 5 consecutive yr in plow-disk and no-tillage corn. Cumulative seed production by 0.19 velvetleaf plants m−2increased in a linear fashion from 1989 to 1994, with annual additions averaging from 330 seeds m−2for velvetleaf in corn to 2,500 seeds m−2for velvetleaf without competition from corn. Five-year cumulative seed production was 1,480 seeds m−2in plow-disk and 1,810 seeds m−2in no-till corn. In no-till corn, 42 velvetleaf seedlings m−2emerged the 1st year after the 1989 seed rain, but only 35 seedlings m−2emerged over the next 4 yr. In plow-disk plots, annual emergence averaged 12 seedlings m−2. Five years after the 1989 seed rain, the proportion of seeds lost to emergence was about 20% in both tillage treatments. Where velvetleaf seeds were allowed to return to the soil every year, cumulative seedling emergence was lower in plow-disk than in no-till corn, with total emergence of 70 and 360 seedlings m−2, respectively, after 5 yr. Seedbank numbers ranged from 10 seeds m−25 yr after a single seed rain (290 seeds m−2) by velvetleaf in plow-disk corn to 1,020 seeds m−2following 5 consecutive yr of seed rain where 12,580 seeds m−2were returned without corn competition in no-till. Seedbank samples in the fall of the 5th year had 69 to 98% fewer seeds than were accounted for by cumulative seed rain and seedling emergence, with greater apparent seed losses in plow-disk corn than in no-till corn. Over 90% velvetleaf control would be required annually to maintain subthreshold populations for 5 yr following a single seed rain. By comparison, over 95% control would be required annually to maintain subthreshold populations where velvetleaf seed return is permitted each year.

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Seed Rain, Soil Seed Bank, and Seedling Emergence Indicate Limited Potential for Self-Recovery in a Highly Disturbed, Tropical, Mixed Deciduous Forest

Plants ◽

10.3390/plants9101391 ◽

2020 ◽

Vol 9 (10) ◽

pp. 1391

Author(s):

Anussara Chalermsri ◽

La-aw Ampornpan ◽

Witoon Purahong

Keyword(s):

Mortality Rate ◽

Seed Bank ◽

Tree Species ◽

Deciduous Forest ◽

Soil Seed Bank ◽

Seedling Emergence ◽

Seed Rain ◽

Reproductive Phenology ◽

Mixed Deciduous Forest ◽

Standing Vegetation

Human activity negatively affects the sustainability of forest ecosystems globally. Disturbed forests may or may not recover by themselves in a certain period of time. However, it is still unclear as to what parameters can be used to reasonably predict the potential for self-recovery of human-disturbed forests. Here, we combined seed rain, soil seed bank, and seed emergence experiments to evaluate the potential for self-recovery of a highly disturbed, tropical, mixed deciduous forest in northeastern Thailand. Our results show a limited potential for self-recovery of this forest due to low seedling input and storage and an extremely high mortality rate during the drought period. There were 15 tree species of seedlings present during the regeneration period in comparison with a total number of 56 tree species in current standing vegetation. During the dry season, only four tree seedling species survived, and the highest mortality rate reached 83.87%. We also found that the correspondence between the combined number of species and composition of plant communities obtained from seed rain, soil seed bank, and seedling emergence experiments and the standing vegetation was poor. We clearly show the temporal dynamics of the seed rain and seedling communities, which are driven by different plant reproductive phenology and dispersal mechanisms, and drought coupled with mortality. We conclude that this highly disturbed forest needs a management plan and could not recover by itself in a short period of time. We recommend the use of external seed and seedling supplies and the maintenance of soil water content (i.e., shading) during periods of drought in order to help increase seedling abundances and species richness, and to reduce the mortality rate.

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Invertebrate Seed Predators Reduce Weed Emergence Following Seed Rain

Weed Science ◽

10.1614/ws-d-15-00111.1 ◽

2016 ◽

Vol 64 (1) ◽

pp. 80-86 ◽

Cited By ~ 11

Author(s):

Carmen K. Blubaugh ◽

Ian Kaplan

Keyword(s):

Seed Predation ◽

Cover Crops ◽

Cover Crop ◽

Propagule Pressure ◽

Seedling Emergence ◽

Seed Rain ◽

Weed Species ◽

Seed Predator ◽

Common Lambsquarters ◽

Seed Predators

Weeds are selected to produce overwhelming propagule pressure, and while vertebrate and invertebrate seed predators destroy a large percentage of seeds, their ecosystem services may not be sufficient to overcome germination site limitations. Cover crops are suggested to facilitate seed predation, but it is difficult to disentangle reductions in weed recruitment attributable to granivores from those due to plant competition. Using common lambsquarters as a focal weed species, we used experimental seed subsidies and differential seed predator exclusion to evaluate the utility of vertebrate and invertebrate seed predators in fallow, killed cover crop, and living mulch systems. Over two growing seasons, we found that seed predators were responsible for a 38% reduction in seedling emergence and 81% reduction in weed biomass in fallow plots following simulated seed rain, suggesting that granivory indeed overcomes safe-site limitation and suppresses weeds. However, the common lambsquarters densities in ambient seedbanks across fallow and cover crop treatments were high, and seed predators did not impact their abundance. Across the study, we found either neutral or negative effects of vertebrate seed predators on seed predation, suggesting that invertebrate seed predators contribute most to common lamnsquarters regulation in our system. These results imply that weed seed biocontrol by invertebrates can reduce propagule pressure initially following senescence, but other tools must be leveraged for long-term seedbank management.

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QuickSCAT observations of extreme wind events over the Mediterranean and Black Seas during 2000-2008

International Journal of Climatology ◽

10.1002/joc.2213 ◽

2010 ◽

Vol 31 (14) ◽

pp. 2068-2077 ◽

Cited By ~ 23

Author(s):

Themis Chronis ◽

V. Papadopoulos ◽

E. I. Nikolopoulos

Keyword(s):

Extreme Wind ◽

The Mediterranean ◽

Wind Events ◽

Mediterranean And Black Seas

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Model projected changes of extreme wind events in response to global warming

Geophysical Research Letters ◽

10.1029/2009gl037500 ◽

2009 ◽

Vol 36 (10) ◽

Cited By ~ 62

Author(s):

G. Gastineau ◽

B. J. Soden

Keyword(s):

Global Warming ◽

Extreme Wind ◽

Wind Events ◽

Projected Changes

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WIND TURBULENCE OVER SEAS IN TROPICAL CYCLONES

Coastal Engineering Proceedings ◽

10.9753/icce.v18.25 ◽

1982 ◽

Vol 1 (18) ◽

pp. 25

Author(s):

W.H. Melbourne ◽

D.R. Blackman

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Turbulence Intensity ◽

Land Surface ◽

Wind Loading ◽

Wind Flow ◽

Atmospheric Conditions ◽

Surface Drag ◽

Extreme Wind ◽

Design Calculations

A study of wind data collected from the Waglan Island anemometer (Hong Kong) during 39 tropical cyclones indicates that turbulence intensity values in excess of 20% at a reference height of 50 m are likely during extreme wind conditions in a tropical cyclone. The implied surface drag coefficient of approximately 0.01 in these extreme wind conditions is consistent with wind flow over a land surface roughness of trees and suburban housing, but is much higher (by a factor of five) than that predicted by the currently accepted formulae from the reviews of Garratt and Wu for wind flow over a fully developed sea in neutral atmospheric conditions. For wind loading design calculations in extreme wind in tropical cyclone conditions it is recommended that mean wind and turbulence intensity profiles should be calculated with a roughness length zQ = 0.20 m in the Deaves and Harris wind model.

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